I have a 3 year old application I elected not to have published. Assuming no prior art has come up in the mean time what is the latest and cheapest option to be able to offer a potential buyer the ability to obtain foreign patents on the same invention?
You are going to have a heck of a time explaining to the USPTO why you requested non-publication of the U.S. case if you later seek patent rights in a foreign country. The primary basis of the PTO agreeing not to publish your U.S. non-provisional application is a statement by the applicant that the invention disclosed in the U.S. application will not be the subject of an application filed in another country requiring publication of applications 18 months after filing (which is a lot of countries).
35 U.S.C. b(2)B(i):
"If an applicant makes a request upon filing, certifying that the invention disclosed in the application has not and will not be the subject of an application filed in another country, or under a multilateral international agreement, that requires publication of applications 18 months after filing, the application shall not be published as provided in paragraph (1)."
"37 CFR 1.213. Nonpublication request.
(a) If the invention disclosed in an application has not been and will not be the subject of an application filed in another country, or under a multilateral international agreement, that requires publication of applications eighteen months after filing, the application will not be published under 35 U.S.C. 122(b) and § 1.211 provided:
(1) A request (nonpublication request) is submitted with the application upon filing;
(2) The request states in a conspicuous manner that the application is not to be published under 35 U.S.C. 122(b);
(3) The request contains a certification that the invention disclosed in the application has not been and will not be the subject of an application filed in another country, or under a multilateral international agreement, that requires publication at eighteen months after filing; and
(4) The request is signed in compliance with § 1.33(b)."
Of course, you can always rescind the non-publication request, but based on your post here the certification you made to the PTO could be called into question. See the following:
" A certification under 37 CFR 1.213(a)(3) cannot be made based on a lack of knowledge of the applicant’s plans concerning the filing of any counterpart application that would be subject to eighteen-month publication or the applicant’s past practices or tendencies with respect to the filing of foreign counterpart applications. The fact that a particular applicant has a tendency to file counterpart applications for fewer than fifty percent of its U.S. applications is not alone an adequate basis for filing all or any of the U.S. applications with a nonpublication request. The applicant must have an affirmative intent not to file a counterpart application, and not just the absence of any intent or plan concerning the filing of any counterpart application that would be subject to eighteen-month publication. A nonpublication request is only appropriate if the applicant’s intent at the time the nonpublication request is being filed is not to file a counterpart foreign or international application that would be subject to eighteen-month publication"